Hi, I have bene looking for a rappelling rope for traversing the rocky area where I live when I go on hikes. I am very light weight (117) and so I dont need a thick rope. I am split between this sterling tag line 7mm: http://www.backcountry.com/sterling-tag ... 69-OR-S75M
and this mammut 6mm rappell cord: http://www.mammut.ch/store/US/en_US/B2C ... -1037-1040
for about the same price, you can get 40m of the 6mm cord and 75m of the 7mm cord. Do you guys know why this is? What makes the mammut cord so special?

From a friction standpoint, 6 mm is really small for rappelling. You should be proficient with rappels before trying even a 7 mm cord.

What device/technique are you going to use? What anchor setup?
Tag lines are generally used in conjunction with a lead rope to facilitate full length raps. In that situation the tag is not really weighted much, its just used to retrieve the lead line.
A 6mm aramid line used with a regular tuber device will be pretty, um, invigorating.
Rapelling is generally the most dangerous part of any climb.

Yea I thought 6mm would be too skinny but Mammut is being extremely clear that this rope is designed for rappelling, which I don't think they would do unless they are confident about the ropes ability. I was planning on using a sterling ATS and or an atc-xp.

I was also looking at the sterling 9mm safetypro, but because I'm going to have to be carrying around frequently I'd like to keep weight down. Can you guys recommend a good 8mm/7mm rope? Also, so the 7mm tag line I mentioned can't be used independently for a double line rappel?

You don't make it clear how long a rope you need, and if you will be using in in low-stress situations as an emergency item.

There was a similar thread some time back.
abseiling-rappelling-descender-for-skinny-cord-t67112-15.html

Most normal devices (such as ATCs) will not work with rope less than 8mm. You can buy fairly cheap semi-static 8mm nylon "cord" from sterling or bluewater; it will work with a normal atc, aided by threading it through an extra carabiner on your leg loop. 100' of this rope weighs a bit over 3 lbs.

I have rapped using 7mm cord and a munter hitch. The munter will tend to twist double ropes (especially if tied at the end). In my mind, the slight savings in weight over 8mm is not worth the scariness of a rap out of control.

In an emergency. I've rapped off 15mm tubular climb-spec webbing. 100' is below 2 lbs, and achieves enough friction in an atc or munter. However, I recommend this ONLY for emergencies.

One should gain a fair amount of experience with raps, and if you want to experiment, go to a place that has a steep but non-vertical slope to try ANY new combination. It's best to start an "experimental" rap on a gradually increasing slope, so you can weight the rope and bail early if something seems wrong. Better yet, practice from a tree in your backyard, with just 5-10' free.

Usually, a tagline is tied to the thicker rope so it cannot be weighted in preference to the thicker rope; often there is a carabiner block on the 7mm side of the rap ring or rapide. It may be put through the other side of the atc to keep it in control during the rap.

I need about a 40-50 meter rope, but I dont mind buying a longer one and then cutting it. Skinnier rope would work fine with a device like an ATS, no? Also, do you know if the sterling accessory cord has been used to rappel safely? Their website warns against it.

http://www.sterlingrope.com/c/climbing_ ... 114346.0.0
what about an "escape rope" such as this?

spegasus wrote:http://www.sterlingrope.com/c/climbing_escape-search-ropes_8mm-per?pkey=3a1861259d6222dc94f139f877548da3&ckey=1114670.1103024.1114346.0.0
what about an "escape rope" such as this?

That looks pretty good, just realize it is a semi-static rope. Most stores will tell you their-off the spool rope is not meant for rappelling. Make sure what you buy has a similar tensile strength and elongation as ropes specifically sold for rappelling. I'm not going to assure you that you will be fine, use common sense. Take a class if you haven't already. Bluewater and Sterling don't get UIAA approval for most of their off-the-spool ropes, because they would have to keep much more stringent manufacturing standards every time there was a color or weaving pattern change. An off-the-spool "8mm" cord may vary by +/- 5% in the tensile strength.

I've tried 3 types of atcs with 8 mm rope, and all worked reasonably well. NONE worked with 7mm rope. Definitely get used to rappelling on 8mm in a safe place before using it in "the wild."

What will you anchors be, trees? Are you going to leave slings with quicklinks or rap rings?

By the time you get a decent atc and harness, the difference in rope weight will seem less important.

The steepness and the length of the rappel are important too. On low angle rock, 45-60 degrees, skinny ropes and ATCs will work okay, but a bit scary. But, as soon as the rocks becomes steep, 80-90 degrees, you need beefier rope, at least 8mm.

As many people here are pointing out, make sure your anchor is good. The chances of anchor failing is probably greater than the rope breaking.

MoapaPk wrote:You don't make it clear how long a rope you need, and if you will be using in in low-stress situations as an emergency item.

Emergencies tend to be high-stress...

Nikolas_A wrote:

MoapaPk wrote:You don't make it clear how long a rope you need, and if you will be using in in low-stress situations as an emergency item.

Emergencies tend to be high-stress...

I meant low tensile stress, as on a non-vertical slope.